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Session 42 - Molecular Clouds: Models and Observations.
Display session, Tuesday, June 11
We report recent 1.67 and 5.00 GHz observations made with the Very Long Baseline Array (VLBA) of five compact extragalactic radio sources viewed through the plasma environment associated with the Cygnus OB1 star formation region. Similar, previously published observations of the source 2013+370 provide a total of six lines of sight through the association. From our data, we extract ments of the scattering measure, \int C_N^2 for all five of the new sources. The data are of particularly good quality for the sources 2005+372 and 2020+351. From these observation, we obtain five conclusions about the nature of scattering through this region. The magnitude of radio wave scattering is enhanced relative to most lines of sight in the sky, including many at low galactic latitudes. (2) The radio wave scattering is spatially variable, showing substantial variations from one line of sight to another. (3) In the case of the two best-observed cases, the measured phase structure function indicates a Kolmogorov spectrum of plasma density fluctuations. (4) The scattering is anisotropic, indicating that the density fluctuations are elongated, probably by the interstellar magnetic field. (5) We confirm and extend a previously reported relationship between emission measure and scattering measure, although there is a great deal of dispersion in the relation. We will discuss possible reasons for this dispersion.
Program listing for Tuesday